1. Technical Field
The present invention appertains generally to extracorporeal pumps, and more specifically to a pumping chamber for an extracorporeal pumping device.
There are a number of medical procedures which require that the pumping duties of the human heart be circumvented, and that these duties be assumed by mechanical means. While there are many available pumps, the best-known types utilize one or more rollers and a length of tubing termed the pumping chamber which carries the blood. Typically, as the rollers of the mechanical pump squeeze the tubing or pumping chamber shut, blood or other biologic fluid is transported through the tubing and is eventually returned to the patient. During many medical procedures such as coronary by-pass-type surgery, prolonged extracorporeal pumping is necessary.
The above-described roller-single tube pumping devices present recognized dangers to the patient. These pumping devices which possess pumping chambers composed of single tubing elements tend to "run dry," that is, to continue pumping even when no blood is being transported therethrough. The reason for this phenomenon is that the single tube of the standard pumping chamber has great mechanical strength, necessary to absorb and recover from the constant shock of the roller assembly; decreased pressure within the tube caused by the absence of blood is not sufficient to overcome the mechanical strength of the tubing, cause its collapse, and cease the pumping action. With presently available devices, inadequate blood volumes result in the formation of a suction through continued pumping, exposing the patient to the possible introduction of an air embolism or the dangers of negative flow.
Heretofore, solutions to the above-stated problems have remained elusive, underscoring the longstanding need for an extracorporeal pumping device that responds to inadequate blood flow rates. The instant invention presents the user with an alternate pumping chamber to be used in a roller-type devices which enables the user to read changes in the patient's blood pressure and to utilize a pumping device that occludes in the presence of inadequate blood volume.
2. Prior Art
The prior art relating to extracorporeal pumping devices is primarily composed of many devices which rely on rollers and single-tube pumping chambers. As stated hereinabove, such devices suffer from well-recognized deficiencies which may cause harm to the patient. Recently, Austin et al. (U.S. Pat. No. 4,515,589)have modified the standard single-tube perfusion loop or single-tube pumping chamber by making a pumping section comprised of a thin-walled inner tube positioned in a thick-walled outer tube, the annular space created by the overlay being vented to the atmosphere. It is further disclosed, that the inner tube will collapse in response to inadequate volumes of blood, the collapse pressure of the inner tube being predicated upon atmospheric pressure.